1. Field of the Invention
The present invention relates to a projector device using a digital mirror device (hereinafter may be referred simply to as a xe2x80x9cDMDxe2x80x9d) having a plurality of mirror elements and a method for correcting a video signal being used in the digital mirror device projector, and more particularly to the DMD projector that makes effective use of light being reflected while each of the mirror elements is turned OFF and a method for correcting the video signal being used in the digital mirror device projector.
The present application claims priority of Japanese Patent Application No. 2002-080853 filed on Mar. 22, 2002, which is hereby incorporated by reference.
2. Description of the Related Art
A DMD (Digital Mirror Device) projector is generally known which uses a DMD panel having several hundreds of thousand of mirror elements each being able to control an inclination for being mounted being placed on a semiconductor memory cell and which controls a reflection state by exerting control on the inclination of each of the mirror elements to form an image, which is disclosed in, for example, Japanese Patent Application Laid-open No. Hei 10-78550.
In the disclosed DMD projector, light emitted from a light source is configured to be condensed as a spot on a color wheel, being made up of a plurality of kinds of color filters adapted to selectively let any one of red, green, and blue color light pass and light having passed through any one of the color filters is applied, in a form of a parallel luminous flux, on the DMD panel and image light being light reflected off the DMD panel is projected through a zoom projection lens onto a screen.
However, the conventional DMD projector has problems. That is, in the above-described conventional DMD projector, light which passes through the color filters making up the color wheel and is reflected off a surface of the DMD panel towards the screen is used as image light. As a result, a wavelength component of each color light serving a source of image light is made different depending on variations in performance of the color filters making up the color wheel. Moreover, even when performance of the color filter is uniform between different filters, if light itself emitted from the light source has variations in wavelength or in intensity, the wavelength component of each color light is also made different and, even if image light is made up of a same video signal, it is difficult to calibrate image light so as to have same chromaticness (tint) among different devices.
In view of the above, it is an object of the present invention to provide a DMD projector using a DMD (Digital Mirror Device) panel which is capable of individually measuring intensity of each light of color being reflected while a mirror element is turned OFF and of correcting a video signal based on a result of the measurement, thus enabling each projector to provide an image having the same chromaticness (tint).
It is another object of the present invention to provide a method for correcting a video signal being used in the DMD projector.
According to a first aspect of the present invention, there is provided a digital mirror device projector including:
a light source;
a color wheel configured by combining a plurality of kinds of color filters for making image light of a plurality of colors;
a digital mirror device panel having a plurality of mirror elements each being controlled so as to be put in a first inclination state and in a second inclination state and reflecting light fed from the light source and passed through any one of the color filters making up the color wheel while being put in the first inclination state, as the image light, in a first direction and reflecting light fed from the light source and passed through any one of the color filters making up the color wheel while being put in the second inclination state in a second direction being different from the first direction;
a driving unit to control so as to put each of the mirror elements in the digital mirror device panel in the first inclination state or the second inclination state according to a corresponding video signal and a revolution state of the color wheel;
a photoelectric conversion device being placed as a photosensor in such a position where light reflected from at least one of the mirror elements is incident when the at least one of the mirror elements is in the second inclination state and, whereby the photoelectric conversion device receives the reflected light and converts the received light to a voltage;
a correcting unit to receive a video signal and the voltage obtained by the photoelectric conversion device, to correct the video signal, based on the received voltage and to output the corrected video signal to the driving unit.
In the foregoing first aspect, a preferable mode is one wherein the color wheel is configured by combining a red color filter, a green color and a blue color filter for making image light of the plurality of colors.
Also, a preferable mode is one wherein the driving unit controls so as to put the at least one of the mirror elements in the digital mirror device panel in the first inclination state or the second inclination state according to the corrected video signal and a revolution state of the color wheel.
Also, a preferable mode is one wherein the correcting unit calculates a relative intensity of light of color having passed through each of the color filters making up the color wheel, based on the voltage output from the photoelectric conversion device occurring when the at least one of the mirror elements of the digital mirror device panel is put in the second state, determines a weighted value to the light of color having passed through each of the color filters so that the relative intensity of the light of color is matched to a predetermined reference value, corrects a luminance signal for each color of a video signal using the weighted value and outputs the corrected luminance signal to the driving unit.
According to a second aspect of the present invention, there is provided a digital mirror device projector including:
a light source;
a color wheel configured by combining a plurality of kinds of color filters for making image light of a plurality of colors;
a digital mirror device panel having a plurality of mirror elements each being controlled so as to be put in a first inclination state and in a second inclination state and reflecting light fed from the light source and passed through any one of the color filters making up the color wheel while being put in the first inclination state, as the image light, in a first direction and reflecting light fed from the light source and passed through any one of the color filters making up the color wheel while being put in the second inclination state in a second direction being different from the first direction;
a driving unit to control so as to put each of the mirror elements in the digital mirror device panel in the first inclination state or the second inclination state according to a corresponding video signal and a revolution state of the color wheel;
a photoelectric conversion device being placed as a photosensor in such a position where light reflected from each of the mirror elements is incident when each of the mirror elements is in the second inclination state and, whereby the photoelectric conversion device receives the reflected light and converts the received light to a voltage;
a correcting unit to receive a video signal and the voltage obtained by the photoelectric conversion device, to correct the video signal, based on the received voltage and to output the corrected video signal to the driving unit.
According to a third aspect of the present invention, there is provided a method for correcting a video signal to be used in a digital mirror device projector made up of a light source, a color wheel configured by combining a plurality of kinds of color filters for making image light of a plurality of colors, a digital mirror device panel having a plurality of mirror elements each being controlled so as to be put in a first inclination state and in a second inclination state and reflecting light fed from the light source and passed through any one of the color filters making up the color wheel while being put in the first inclination state, as the image light, in a first direction and reflecting light fed from the light source and passed through any one of the color filters making up the color wheel while being put in the second inclination state in a second direction being different from the first direction, and a driving unit to control so as to put each of the mirror elements in the digital mirror device panel in the first inclination state or the second inclination state, the method including:
a step of placing a photoelectric conversion device as a photo-sensor in such a position where light reflected from at least one of the mirror elements is incident when the at least one of the mirror elements is in the second inclination state and, whereby the photoelectric conversion device receives the reflected light and converts the received light to a voltage;
a step of having a correcting unit receive a video signal and the voltage obtained by the photoelectric conversion device, correct the video signal, based on the received voltage and output the corrected video signal to the driving unit; and
a step of having the driving unit control so as to put the at least one of the mirror elements in the digital mirror device panel in the first inclination state or the second inclination state according to the corrected video signal and a revolution state of the color wheel.
In the foregoing second aspect, a preferable mode is one wherein the color wheel is configured by combining a red color filter, a green color and a blue color filter for making image light of the plurality of colors.
Also, a preferable mode is one wherein the correcting unit calculates a relative intensity of light of color having passed through each of the color filters making up the color wheel, based on the output voltage from the photoelectric conversion device occurring when the at least one of the mirror elements of the digital mirror device panel is put in the second state, determines a weighted value to the light of color having passed through each of the color filters so that the relative intensity of the light of color is matched to a predetermined reference value, corrects a luminance signal for each color of a video signal using the weighted value and outputs the corrected luminance signal to the driving unit.
According to a fourth aspect of the present invention, there is provided a method for correcting a video signal to be used in a digital mirror device projector made up of a light source, a color wheel configured by combining a plurality of kinds of color filters for making image light of a plurality of colors, a digital mirror device panel having a plurality of mirror elements each being controlled so as to be put in a first inclination state and in a second inclination state and reflecting light fed from the light source and passed through any one of the color filters making up the color wheel while being put in the first inclination state, as the image light, in a first direction and reflecting light fed from the light source and passed through any one of the color filters making up the color wheel while being put in the second inclination state in a second direction being different from the first direction, and a driving unit to control so as to put each of the mirror elements in the digital mirror device panel in the first inclination state or the second inclination state, the method including:
a step of placing a photoelectric conversion device as a photo-sensor in such a position where light reflected from each of the mirror elements is incident when each of the mirror elements is in the second inclination state and, whereby the photoelectric conversion device receives the reflected light and converts the received light to a voltage;
a step of having a correcting unit receive a video signal and the voltage obtained by the photoelectric conversion device, correct the video signal, based on the received voltage and output the corrected video signal to the driving unit; and
a step of having the driving unit control so as to put each of the mirror elements in the digital mirror device panel in the first inclination state or the second inclination state according to the corrected video signal and a revolution state of the color wheel.
By configuring the projector using the DMD panel as above, light having passed through the color wheel is incident on the DMD panel. An inclination state of each of the mirror elements on the DMD panel is controlled according to a video signal. An angle at which light is reflected is changed according to an ON or OFF state, where light reflected in the ON state travels toward a projection lens and light reflected in the OFF state is input to the photoelectric conversion device and is converted to an electrical signal representing intensity of light to be output from the photoelectric conversion device.
At this point, as a specified pattern for projection, for example, by projecting an image with 100% of red light projected on the screen and 0% applied to the photoelectric conversion device and with 100% of green light projected on the screen and 0% applied to the photoelectric conversion device and with 0% of blue light projected on the screen and 100% applied to the photoelectric conversion device, relative intensity of the blue light can be measured. By using the same method as above, intensity of red or green light can be measured sequentially. Thus, same chromaticness can be provided on an image to be projected on the screen by controlling the DMD panel through the panel driving unit after having made correction on each level of video signals using data on the intensity of red, green, and blue light as correction data in the correcting unit.
With the above configurations, since brightness of red, green, and blue color light for an image can be easily matched, it is possible that chromaticness is provided at a same level. No correction of the video signal by individually using an optical device with its light source being replaced is required.